On 18 Feb 2021, at 20:52, Konstantin Belousov <kostik...@gmail.com> wrote: > On Wed, Feb 17, 2021 at 04:48:22PM -0800, John Baldwin wrote: >> On 2/17/21 4:35 PM, John Baldwin wrote: >>> The branch main has been updated by jhb: >>> >>> URL: >>> https://cgit.FreeBSD.org/src/commit/?id=24fd63e0970f91189dd2acde987bd2e4c8c04a50 >>> >>> commit 24fd63e0970f91189dd2acde987bd2e4c8c04a50 >>> Author: John Baldwin <j...@freebsd.org> >>> AuthorDate: 2021-02-18 00:34:23 +0000 >>> Commit: John Baldwin <j...@freebsd.org> >>> CommitDate: 2021-02-18 00:34:23 +0000 >>> >>> mips: Don't set __NO_TLS to disable some uses of TLS. >>> __NO_TLS was originally added to disable use of _Thread in the locale >>> code in libc in 82dd5016bd749d1d9e1531bd1703aebeecceab34. At the time >>> libc did not support TLS on MIPS (I believe), but TLS support was >>> added to libc (at least _set_tp.c) for MIPS about a month after >>> __NO_TLS was added, but __NO_TLS was still left around. >>> Reviewed by: imp >>> Sponsored by: DARPA >>> Differential Revision: https://reviews.freebsd.org/D28713 >>> --- >>> sys/sys/cdefs.h | 3 +-- >>> 1 file changed, 1 insertion(+), 2 deletions(-) >>> >>> diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h >>> index 64f26480a2f5..ff18911f6acf 100644 >>> --- a/sys/sys/cdefs.h >>> +++ b/sys/sys/cdefs.h >>> @@ -768,8 +768,7 @@ >>> #endif >>> #endif /* __STDC_WANT_LIB_EXT1__ */ >>> -#if defined(__mips) || \ >>> - (defined(__powerpc64__) && (!defined(_CALL_ELF) || _CALL_ELF == 1)) >>> +#if defined(__powerpc64__) && (!defined(_CALL_ELF) || _CALL_ELF == 1) >>> #define __NO_TLS 1 >>> #endif >> >> It would be really nice to kill __NO_TLS entirely. There is at least one >> unconditional use of _Thread_local (sorry, should have used that instead >> of _Thread above) in libc in stdlib/cxa_thread_atexit_impl.c, so it seems >> highly unlikely that TLS is actually broken on any of our platforms as the >> libc build would have been broken instead. > > There is a difference between compile and runtime. The mentioned libc > use in cxa_thread_atexit_impl.c is to support some (I believe) rarely > used C++ feature of thread-local storage with destructors, so it might > be simply not observed often. OTOH, locale functions infect almost > everything string-related in libc, so the breakage would be quite > visible.
It's also used in jemalloc for tsd_initialized which is a rather key variable, so if TLS is broken you won't get very far in userspace (source: I had to debug implementing it for CHERI-MIPS), well before you even think about getting to locale functions. > But, I wonder, what does CALL_ELF mean? Is it for old 64bit PowerPC ABI, > that was abandoned with the switch to ELFv2? Yes, _CALL_ELF == 2 for ELFv2. I highly doubt the defines were needed for the ELFv1 ABI, but they're especially redundant now. Presumably David's original fixed commit[1] added powerpc64 to that list because TLS wasn't yet supported in LLVM; that happened later in 2012 and our wiki changed it to being implemented in December 2012[2]. So I suspect it should have been deleted 8 years ago. Jess [1] b0968176b3a821598a31de6698e01931d1417584 [2] https://wiki.freebsd.org/action/diff/BuildingFreeBSDWithClang?action=diff&rev1=340&rev2=341 _______________________________________________ dev-commits-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/dev-commits-src-all To unsubscribe, send any mail to "dev-commits-src-all-unsubscr...@freebsd.org"
